Description of problem:
When a VM is running, the VMI's resource 'Guest OS Info'  is not available after a number of minutes.

Gguest agent data provided from virtcl is available however the VMI resource one is not.

Version-Release number of selected component (if applicable):
2.6.0-106

How reproducible:
100%

Steps to Reproduce:
1. Start a VM
2. Monitor the VMI resource


Actual results:
When the VMI is running, 'Guest OS Info' is displayed.
 Guest OS Info:
    Id:              rhel
    Kernel Release:  4.18.0-240.12.1.el8_3.x86_64
    Kernel Version:  #1 SMP Wed Jan 13 06:05:15 EST 2021
    Name:            Red Hat Enterprise Linux
    Pretty Name:     Red Hat Enterprise Linux 8.3 (Ootpa)
    Version:         8.3
    Version Id:      8.3
  Interfaces:

After a number of minutes, the information is no longer available (guest agnet info is still avialable via virtctl):
   Type:                  AgentConnected
  Guest OS Info:
  Interfaces:

virtctl guestosinfo rhel8-vm
{
  "guestAgentVersion": "4.2.0",
  "hostname": "rhel8-vm",
  "os": {
    "name": "Red Hat Enterprise Linux",
    "kernelRelease": "4.18.0-240.12.1.el8_3.x86_64",
    "version": "8.3 (Ootpa)",
    "prettyName": "Red Hat Enterprise Linux 8.3 (Ootpa)",
    "versionId": "8.3",
    "kernelVersion": "#1 SMP Wed Jan 13 06:05:15 EST 2021",
    "machine": "x86_64",
    "id": "rhel"
  },
  "timezone": "EST, -18000",
  "fsInfo": {
    "disks": [
      {
        "diskName": "vda2",
        "mountPoint": "/boot/efi",
        "fileSystemType": "vfat",
        "usedBytes": 7170048,
        "totalBytes": 104634368
      },
      {
        "diskName": "vda3",
        "mountPoint": "/",
        "fileSystemType": "xfs",
        "usedBytes": 1602134016,
        "totalBytes": 32094793728
      }
    ]
  }
}

Expected results:
Guset OS info should be consistent and available both in VMI resource and virtctl.

Additional info:
 oc describe vmi rhel8-vm
Name:         rhel8-vm
Namespace:    default
Labels:       kubevirt.io/domain=rhel8-vm
              kubevirt.io/nodeName=ssp01-t6h4t-worker-0-z4qqw
              kubevirt.io/size=tiny
Annotations:  kubevirt.io/latest-observed-api-version: v1alpha3
              kubevirt.io/storage-observed-api-version: v1alpha3
API Version:  kubevirt.io/v1alpha3
Kind:         VirtualMachineInstance
Metadata:
  Creation Timestamp:  2021-02-01T16:21:33Z
  Finalizers:
    foregroundDeleteVirtualMachine
  Generation:  13
  Managed Fields:
    API Version:  kubevirt.io/v1alpha3
    Fields Type:  FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .:
          f:kubevirt.io/latest-observed-api-version:
          f:kubevirt.io/storage-observed-api-version:
        f:labels:
          .:
          f:kubevirt.io/domain:
          f:kubevirt.io/nodeName:
          f:kubevirt.io/size:
        f:ownerReferences:
      f:spec:
        .:
        f:domain:
          .:
          f:cpu:
            .:
            f:cores:
            f:sockets:
            f:threads:
          f:devices:
            .:
            f:disks:
            f:interfaces:
            f:networkInterfaceMultiqueue:
            f:rng:
          f:firmware:
            .:
            f:uuid:
          f:machine:
            .:
            f:type:
          f:resources:
            .:
            f:requests:
              .:
              f:memory:
        f:evictionStrategy:
        f:networks:
        f:terminationGracePeriodSeconds:
        f:volumes:
      f:status:
        .:
        f:activePods:
          .:
          f:d1d993cb-afe4-40e6-b32f-b8d5a144f001:
        f:guestOSInfo:
        f:nodeName:
        f:qosClass:
    Manager:      virt-controller
    Operation:    Update
    Time:         2021-02-01T16:21:38Z
    API Version:  kubevirt.io/v1alpha3
    Fields Type:  FieldsV1
    fieldsV1:
      f:status:
        f:conditions:
        f:interfaces:
        f:migrationMethod:
        f:phase:
        f:volumeStatus:
    Manager:    virt-handler
    Operation:  Update
    Time:       2021-02-01T16:22:13Z
  Owner References:
    API Version:           kubevirt.io/v1alpha3
    Block Owner Deletion:  true
    Controller:            true
    Kind:                  VirtualMachine
    Name:                  rhel8-vm
    UID:                   265981bc-7879-4f7f-9311-a310508e52f3
  Resource Version:        3720164
  Self Link:               /apis/kubevirt.io/v1alpha3/namespaces/default/virtualmachineinstances/rhel8-vm
  UID:                     8e33b9c0-c70b-4616-b0ff-42bc27f80f5f
Spec:
  Domain:
    Cpu:
      Cores:    1
      Sockets:  1
      Threads:  1
    Devices:
      Disks:
        Disk:
          Bus:  virtio
        Name:   rhel8-vm
        Disk:
          Bus:  virtio
        Name:   cloudinitdisk
      Interfaces:
        Masquerade:
        Name:                        default
      Network Interface Multiqueue:  true
      Rng:
    Features:
      Acpi:
        Enabled:  true
    Firmware:
      Uuid:  ee04d89a-59d6-5a2b-9935-6b9f7ec061fd
    Machine:
      Type:  pc-q35-rhel8.3.0
    Resources:
      Requests:
        Cpu:          100m
        Memory:       1536Mi
  Eviction Strategy:  LiveMigrate
  Networks:
    Name:  default
    Pod:
  Termination Grace Period Seconds:  180
  Volumes:
    Data Volume:
      Name:  rhel8
    Name:    rhel8-vm
    Cloud Init No Cloud:
      User Data:  #cloud-config
user: cloud-user
password: jnrt-awuf-tck8
chpasswd: { expire: False }
    Name:  cloudinitdisk
Status:
  Active Pods:
    d1d993cb-afe4-40e6-b32f-b8d5a144f001:  ssp01-t6h4t-worker-0-z4qqw
  Conditions:
    Last Probe Time:       <nil>
    Last Transition Time:  <nil>
    Status:                True
    Type:                  LiveMigratable
    Last Probe Time:       <nil>
    Last Transition Time:  2021-02-01T16:21:37Z
    Status:                True
    Type:                  Ready
    Last Probe Time:       2021-02-01T16:22:13Z
    Last Transition Time:  <nil>
    Status:                True
    Type:                  AgentConnected
  Guest OS Info:
  Interfaces:
    Interface Name:  eth0
    Ip Address:      10.131.1.124
    Ip Addresses:
      10.131.1.124
    Mac:             52:54:00:84:0a:cc
    Name:            default
  Migration Method:  BlockMigration
  Node Name:         ssp01-t6h4t-worker-0-z4qqw
  Phase:             Running
  Qos Class:         Burstable
  Volume Status:
    Name:    cloudinitdisk
    Target:  vdb
    Name:    rhel8-vm
    Target:  vda
Events:
  Type    Reason            Age                   From                         Message
  ----    ------            ----                  ----                         -------
  Normal  SuccessfulCreate  2m18s                 disruptionbudget-controller  Created PodDisruptionBudget kubevirt-disruption-budget-qhxv5
  Normal  SuccessfulCreate  2m18s                 virtualmachine-controller    Created virtual machine pod virt-launcher-rhel8-vm-x8rh9
  Normal  Started           2m13s                 virt-handler                 VirtualMachineInstance started.
  Normal  Created           35s (x14 over 2m13s)  virt-handler                 VirtualMachineInstance defined.